1. Field of the Invention
The present invention relates to a control apparatus of an automatic transmission and, more particularly, to a control apparatus of an automatic transmission designed so as to alter shift patterns in accordance with the kind of fuel used.
2. Description of Prior Art
Generally, as an automatic transmission is widely employed one composed of a combination of a torque converter with a shifting mechanism of a multistage gear set with a gear mechanism such as a planetary gear mechanism.
The shifting control in such an automatic transmission utilizes usually a hydraulic pressure mechanism in which a hydraulic pressure circuit is changed over by an electromagnetic valve to operate a friction element such as a brake, clutch and so on as a hydraulic actuator accompanying with the multistage planetary gear shifting mechanism, thereby switching a system transmitting the engine power and providing a desired shifting range. To shift the hydraulic pressure circuit with the change-over valve, it is usually arranged so as to be selectively operated by means of shift-up signals or shift-down signals from an electronic control apparatus that permits the detection of the running state of a vehicle beyond a predetermined shifting line.
As such means for shifting gears on the basis of predetermined shift patterns, it is known that the shift patterns themselves are altered. U.S. Pat. No. 3,640,156 discloses the alteration of shift patterns in accordance with temperatures of an engine. Specifically, it is designed that a favorable operation efficiency of an engine is insured by altering the shift pattern so as to allow the engine rotations (vehicle speed) to become larger when the temperature of the engine is low.
As another example of altering shift patterns, U.S. Pat. No. 4,523,281 discloses an embodiment in which three shift patterns including a power mode, normal mode and economy mode are predetermined and either one can be arbitrarily selected by an operator's (driver's) choice. In this embodiment, the power mode puts an emphasis most on outputs shifted at a high rotational side while the economy on the saving of fuel or mileage. The normal mode is arranged to indicate a pattern between the other two modes. Furthermore, in this embodiment, the shifting mechanism is connected to an engine outputs shaft through a torque converter with a lockup clutch, enabling an arbitrary selection by means of a manual choice from the three modes including the power mode, economy mode or normal mode as an operating pattern of the lockup clutch, that is, as a lockup pattern.
Turning now to the kind of fuels, it is known that, for example, gasoline can be grouped into two kinds, regular gasoline and high octane gasoline. When compared to the regular gasoline, the high octane gasoline is high in the octane number so that problems with knocking may be reduced. Thus it is used for an engine of the high output type with a high compression ratio. Accordingly, it could be said that an operator (driver) who used high octane gasoline tends to prefer to a powerful running with high acceleration.
If fuels with different calorific values are employed, output characteristic of an engine may also be varied.